Competence refers to the ability of a bacterium to take up environmental DNA. Competence regulation in Bacillus subtilis involves a complex signal transduction network that governs the expression of a large regulon. This regulation is embedded in an even more extensive signal transduction network that governs several additional forms of post-exponential, global gene expression, e.g. sporulation and biofilm formation. Remarkably, competence, sporulation and biofilm formation are expressed bimodally and it is proposed to explore the regulatory mechanisms that govern bimodal gene expression, as well as to discover new examples of this type of expression. Additionally, the logic of the competence network and its relevant molecular interactions will be investigated using genetic, biochemical, microscopic and genomic approaches. In particular, the molecular interactions of the adaptor protein MecA will be studied as well as the modes of action of ComK as a novel transcription factor. The proposed work will also explore regulation on the cellular level, namely the mechanisms responsible for the dynamic localization of DNA uptake proteins to the cell poles. In this renewal application there is a new emphasis on generalizing and/or extending some of the concepts that have emerged from previous studies, particularly involving bimodal gene expression, MecA as a stochastic buffer and the cell biology of competence. PUBLIC HEALTH RELEVANCE: Bacteria exchange genes and in this way can acquire antibiotic resistance and other new capabilities that increase virulence. The direct uptake of environmental DNA (transformation) is an important mechanism of such gene exchange in nature. The proposed work will explore the regulation of the genes that enable the uptake of DNA.